The climate crisis is unfortunately a reality. However, it is easy to assume that every aspect in our changing world is a result of climate change. Assumptions play no role in key environmental assessments and mitigation strategies such as we will see in the upcoming UN climate change COP-26 conference – it’s the science and hard facts that are critical. This week’s research is a prime example for facts that matter. Using model projections combined with satellite data from ESA’s Climate Change Initiative, this latest research shows that the global rise in the temperature of lake water and dwindling lake-ice cover can only be explained by the increase in greenhouse gas emissions since the industrial revolution – in other words, humans are clearly to blame.
According to the paper published Nature GeoscienceRising lake-water temperatures are a sign of human-caused climate change. Also, ice-cover on lakes melts faster and forms later.
Luke Grant, from the Vrije Universiteit Brussel (VUB) and lead author, said, “These physical properties are fundamental to lake ecosystems. As the impacts of climate change continue to increase, we are at risk of severely damaging lake ecosystems. This includes water quality and native fish populations. This would be disastrous for the many ways in which local communities depend on lakes, such as drinking water supply and fishing.”
The research team also predicted how things might develop in the future under different climate conditions.
The graph above shows that in a low-emission scenario, the average warming of lakes is estimated to stabilise at 1.5°C above pre-industrial levels and the duration of ice cover to be 14 days shorter. In a high-emission world, these changes could lead lake temperature to increase by 4.0 °C and have 46 fewer days of ice per year.At the beginning of the project, the authors observed changes in lakes around the world, as depicted in the image of Lake Ontario, based on satellite-derived observations from ESA’s Climate Change Initiative lakes project.
However, the role played by climate change in these trends has not yet been established.
“In other words, we had to rule out the possibility that these changes were caused by the natural variability of the climate system,” says fellow VUB researcher and study co-author Inne Vanderkelen.
The team created multiple computer simulations based on models of lakes worldwide, which they then used to run a variety of climate models. After they had built up the database, they used a method described by the Intergovernmental Panel on Climate Change. After determining the historical impacts of climate change on lakes, they analysed different future climate scenarios.
These results suggest that it is unlikely that recent trends in lake temperatures or ice cover can be explained by natural climate variability.
Researchers also discovered clear similarities between observed changes and model simulations of lakes under a climate influenced with greenhouse gas emissions.
“This is clear evidence that human-induced climate change has an impact on lakes,” says Iestyn Woolway, former ESA Fellow and co-author of the study.
Future projections of lake temperatures and ice coverage unanimously indicate rising trends.
For every 1°C increase in global air temperature, lakes are estimated to warm by 0.9°C and lose 9.7 days of ice cover. The analysis also showed significant differences in how climate change will affect lakes at the end if we take the necessary measures.
“Our results underline the great importance of the Paris Agreement to protect the health of lakes around the world,” said Wim Thiery, VUB climate expert and senior author of the study. “If we manage to drastically reduce our emissions in the coming decades, we can still avoid the worst consequences for lakes worldwide.”
Reference: “Attribution of global lake systems change to anthropogenic forcing” by Luke Grant, Inne Vanderkelen, Lukas Gudmundsson, Zeli Tan, Marjorie Perroud, Victor M. Stepanenko, Andrey V. Debolskiy, Bram Droppers, Annette B. G. Janssen, R. Iestyn Woolway, Margarita Choulga, Gianpaolo Balsamo, Georgiy Kirillin, Jacob Schewe, Fang Zhao, Iliusi Vega del Valle, Malgorzata Golub, Don Pierson, Rafael Marcé, Sonia I. Seneviratne and Wim Thiery, 18 October 2021, Nature Geoscience.